避免glium中的丢帧

Question

我使用glium作为我的opengl绑定，但它不可能获得一个可靠的60fps。

最小的测试用例是

#[macro_use]
extern crate glium;
extern crate clock_ticks;

use glium::Surface;
use glium::glutin;

fn main() {
    use glium::DisplayBuild;

    let display = glutin::WindowBuilder::new()
        .build_glium()
        .unwrap();

    let frames = 60 * 5;
    let trials = 3;

    for _ in 0.. trials {
        let start_ns = clock_ticks::precise_time_ns();
        for _ in 0..frames {
            display.draw().finish().unwrap();
        }

        let duration_ns = clock_ticks::precise_time_ns() - start_ns;
        let duration_s = (duration_ns as f64) / 1_000_000_000f64;
        let fps = (frames as f64) / duration_s;
        let dropped = (duration_s - (frames as f64 * (1f64/60f64))) / (1f64/60f64);

        println!("{} frames in {:.6} seconds = {:.3} fps (estimated {:.1} frames dropped)", frames, duration_s, fps, dropped);
    }
}

我期望60 FPS，但当我运行它(在OSX中)时，经常显示59 FPS。The project is available on github，便于编译和运行。

有没有办法调整glium，使它不会丢弃帧？OSX覆盖了vsync设置，所以不能不等待每一帧之间的vsync。

Answer 1

是的，像@8bitree一样，我怀疑你的测量是错误的，而不是一个实际的问题。在我的系统上，Debian：

steve@warmachine:~/tmp/guess$ cargo run
     Running `target/debug/guess`
300 frames in 4.427656 seconds = 67.756 fps (estimated -34.3 frames dropped)
300 frames in 0.006892 seconds = 43529.834 fps (estimated -299.6 frames dropped)
300 frames in 0.006522 seconds = 45997.412 fps (estimated -299.6 frames dropped)
steve@warmachine:~/tmp/guess$ cargo run
     Running `target/debug/guess`
300 frames in 4.953447 seconds = 60.564 fps (estimated -2.8 frames dropped)
300 frames in 4.999410 seconds = 60.007 fps (estimated -0.0 frames dropped)
300 frames in 1.608712 seconds = 186.485 fps (estimated -203.5 frames dropped)

所以，是的，有些东西有点...很奇怪。